A magnetic recording medium for heat-assisted magnetic recording is provided. A magnetic recording layer includes upper and lower magnetic recording layers. The lower magnetic recording layer has a lower granular structure including lower magnetic crystal grains, and a lower non-magnetic portion, that surrounds the lower magnetic crystal grains, mainly composed of carbon. The upper magnetic recording layer has an upper granular structure including upper magnetic crystal grains, and an upper non-magnetic portion, that surrounds the upper magnetic crystal grains, formed from a material selected from the group consisting of silicon nitride, titanium oxide and titanium nitride.

A magnetic recording medium includes a non-magnetic substrate on which at least a soft magnetic underlayer, an orientation control layer, a perpendicular magnetic layer, and a protective layer are disposed. The perpendicular magnetic layer includes first to fourth magnetic layers. A first exchange coupling control layer is disposed between the first magnetic layer and the second magnetic layer. A second exchange coupling control layer is disposed between the second magnetic layer and the third magnetic layer. Following relations are satisfied where Ku.sub.i is a magnetic anisotropic constant of an i-th magnetic layer, Ms.sub.i is a saturation magnetization of the i-th magnetic layer, and t.sub.1 is a film thickness of the i-th magnetic layer, Ku.sub.1>Ku.sub.2, Ku.sub.2>Ku.sub.3, Ms.sub.1×t.sub.1>Ms.sub.2×t.sub.2, Ms.sub.2×t.sub.2>Ms.sub.3×t.sub.3 r Ku.sub.3<Ku.sub.4, and Ms.sub.3×t.sub.3<Ms.sub.4×t.sub.4.

A magnetic recording medium includes a non-magnetic substrate on which at least a soft magnetic underlayer, an orientation control layer, a perpendicular magnetic layer, and a protective layer are disposed. The perpendicular magnetic layer includes first to fourth magnetic layers. A first exchange coupling control layer is disposed between the first magnetic layer and the second magnetic layer. A second exchange coupling control layer is disposed between the second magnetic layer and the third magnetic layer. Following relations are satisfied where Ku.sub.i is a magnetic anisotropic constant of an i-th magnetic layer, Ms.sub.i is a saturation magnetization of the i-th magnetic layer, and t.sub.1 is a film thickness of the i-th magnetic layer, Ku.sub.1>Ku.sub.2, Ku.sub.2>Ku.sub.3, Ms.sub.1×t.sub.1>Ms.sub.2×t.sub.2, Ms.sub.2×t.sub.2>Ms.sub.3×t.sub.3 r Ku.sub.3<Ku.sub.4, and Ms.sub.3×t.sub.3<Ms.sub.4×t.sub.4.

In a tape recording medium, a sliding layer has an electric resistance of 1×10.sup.8 Ω/sq or less, and contains carbon particles and solid particles. The carbon particles have a primary particle size of 30 nm or less and a BET specific surface area of 100 m.sup.2/g or more. The solid particles have a primary particle size of 100 nm or less, a Mohs' hardness in a range from 2.5 to 8, inclusive, a density of 3 g/cm.sup.3 or more, and a BET specific surface area of 30 m.sup.2/g or more.

A method and system provide a magnetic recording media usable in a magnetic storage device. The magnetic recording media includes a substrate, at least one intermediate layer and a magnetic recording stack for storing magnetic data. The intermediate layer(s) include a majority phase having a first diffusion constant and a secondary phase having a second diffusion constant greater than the first diffusion constant. The magnetic recording stack residing on the intermediate layer such that the at least one intermediate layer is between the substrate and the magnetic recording stack.

A magnetic recording cartridge is provided and including a magnetic recording medium, wherein an average thickness of the magnetic recording medium t.sub.T is 3.5 μm≤t.sub.T≤5.6 μm, a dimensional change amount Δw in a width direction of the magnetic recording medium with respect to a tension change in a longitudinal direction of the magnetic recording medium is 700 ppm/N≤Δw≤20000 ppm, the magnetic recording medium is accommodated in a state of being wound around the reel in the cartridge case and (a servo track width on an inner side of winding of the magnetic recording medium)−(a servo track width on an outer side of winding of the magnetic recording medium)>0 is satisfied, and a squareness ratio measured in a vertical direction of the magnetic recording medium is 65% or more.

A magnetic recording cartridge is provided and including a magnetic recording medium, wherein an average thickness of the magnetic recording medium t.sub.T is 3.5 μm≤t.sub.T≤5.6 μm, a dimensional change amount Δw in a width direction of the magnetic recording medium with respect to a tension change in a longitudinal direction of the magnetic recording medium is 700 ppm/N≤Δw≤20000 ppm, the magnetic recording medium is accommodated in a state of being wound around the reel in the cartridge case and (a servo track width on an inner side of winding of the magnetic recording medium)−(a servo track width on an outer side of winding of the magnetic recording medium)>0 is satisfied, and a squareness ratio measured in a vertical direction of the magnetic recording medium is 65% or more.

An insulator-coated soft magnetic powder includes a plurality of particles each including a core which contains a soft magnetic material, and an insulating layer which is provided on the surface of the core and contains a glass material including Bi.sub.2O.sub.3 as a main component. The content of an alkali metal in the insulating layer is 5 mol % or less. The glass material further contains at least one of ZnO and B.sub.2O.sub.3. The content of Bi.sub.2O.sub.3 in the glass material is 40 mol % or more and 80 mol % or less.

An insulator-coated soft magnetic powder includes a plurality of particles each including a core which contains a soft magnetic material, and an insulating layer which is provided on the surface of the core and contains a glass material including Bi.sub.2O.sub.3 as a main component. The content of an alkali metal in the insulating layer is 5 mol % or less. The glass material further contains at least one of ZnO and B.sub.2O.sub.3. The content of Bi.sub.2O.sub.3 in the glass material is 40 mol % or more and 80 mol % or less.

An object is to provide a magnetic recording medium having excellent traveling stability and a thin total thickness.

The present technology provides a tape-shaped magnetic recording medium including: a magnetic layer; an underlayer; a base layer; and a back layer, in which a surface on a side of the magnetic layer has a kurtosis of 3.0 or more, a surface on a side of the back layer has a kurtosis of 2.0 or more, the surface on the magnetic layer side has arithmetic average roughness R.sub.a of 2.5 nm or less, the base layer includes a polyester as a main component, the magnetic recording medium has an average thickness t.sub.T of 5.6 μm or less, the magnetic recording medium includes a lubricant, the lubricant includes a fatty acid and a fatty acid ester, and a mass ratio between the fatty acid and the fatty acid ester extracted with hexane satisfies fatty acid/fatty acid ester ≤0.6, and the magnetic recording medium has pores, and the pores have an average diameter of 6 nm or more and 11 nm or less when the diameters of the pores are measured in a state where the lubricant has been removed from the magnetic recording medium and the magnetic recording medium has been dried.